US President Barack Obama makes $3.68 million in 2008

US PRESIDENT Barack Obama and his wife Michelle made $US2.65 million ($3.68 million) in 2008, mostly from royalties of his two best-selling books, the White House said.

The Obamas and vice president Joe Biden and his wife Jill released their tax returns on the April 15 deadline for Americans to file their 2008 income tax documents.

In their joint return, the President and his wife declared an adjusted gross income of $US2,656,902 and paid $US855,323 ($1.1 million) in federal income tax, as well as $US77,883 ($A108,000) in Illinois state income taxes.

The White House said that the Obamas reported donating $US172,050 ($A236,000) to 37 charities, equivalent to about 6.5 per cent of their adjusted gross income.

The tax forms were filed earlier this month and show the Obamas current occupations as "US President'' and "US First Lady''.

Mr Obama's autobiography Dreams from My Father has spent 142 weeks on the New York Times paperback bestseller list, and his political manifesto The Audacity of Hope has been on the same chart for 67 weeks.

Both works were also global publishing successes, with sales fuelled by Obama's historic and victorious White House campaign last year.

The Obamas reported income of $US4.2 million ($5.7 million) on their 2007 tax return.

The Bidens meanwhile reported 2008 adjusted gross income of $US269,256 ($370,000), mostly through the vice president's former salary as a senator from Delaware and from royalties of his own book.